docs: def is_prime(n):
      """
      is_prime returns True if N is a prime number, False otherwise
  
      Parameters:
         Input, integer N, the number to be checked.
  
         Output, boolean value, True or False
      """
      if n != int(n) or n < 2:
          return False
      if n == 2 or n == 3:
          return True
      if n % 2 == 0 or n % 3 == 0:
          return False
      # All primes >3 are of the form 6n+1 or 6n+5 (6n, 6n+2, 6n+4 are 2-divisible, 6n+3 is 3-divisible)
      p = 5
      root = int(np.ceil(np.sqrt(n)))
      while p <= root:
          if n % p == 0 or n % (p + 2) == 0:
              return False
          p += 6
      return True